Moving a Newsletter List to beehiiv, Kit or Substack: Clean It First

Before importing a newsletter list into beehiiv, Kit or Substack, export only active subscribers, remove anyone who unsubscribed, bounced or complained, verify the remaining addresses, and send your first issue on the new platform to the most engaged readers. Platforms may review large imports, and a bad first send on a new platform can trigger checks or hurt deliverability.

Why a platform switch is risky for deliverability

On your old platform, the list had history: bounces were already handled and sending reputation was established. On the new one:

• The platform has no record of your list's quality.
• Imports are often reviewed, especially large ones.
• The first few sends are watched closely for bounces and complaints.

Switching email platforms covers this in general; this guide is specific to newsletter tools.

Step 1: Export the right segments

From your current platform, export statuses separately:

Segment	What to do
Active subscribers	Clean and import
Unsubscribed	Do not import as active; some platforms let you import as unsubscribed to block re-adds
Hard bounced or cleaned	Do not import
Spam complaints	Do not import
Inactive for a long time	Consider leaving out or re-engaging first

If your old platform is Mailchimp, see Mailchimp cleaned contacts for what each status means.

Step 2: Confirm the list is permission-based

Every newsletter platform requires that subscribers opted in. Purchased lists, scraped addresses, or contacts from an event you did not collect consent from do not belong in an import, and verification does not change that. Should you buy an email list explains the deliverability side.

Step 3: Clean and verify

1. Dedupe with the duplicate email remover.
2. Fix obvious typos like gmial.com with the email typo corrector.
3. Verify every address. Remove invalid; keep disposable addresses out; decide on catch-all.
4. Keep your custom fields (signup date, source, tags) so segmentation survives the move.

There are platform-specific guides for verifying exports from beehiiv, Substack and Kit.

Step 4: Import in a sensible order

Order	Segment
First	Subscribers who opened or clicked recently
Second	Other verified active subscribers
Later or never	Long-inactive subscribers, after re-engagement

If the platform lets you tag imports, tag by source and engagement so you can send to the best segment first.

Step 5: Make the first send count

• Send your first issue on the new platform to recent, engaged readers.
• Tell readers about the move in the last issue on the old platform, including the new sender name and address, so they recognise it.
• Watch bounces and complaints on the first two or three sends before widening.

Gmail's and Yahoo's sender requirements still apply after the move; see bulk sender requirements. Make sure your sending domain is authenticated on the new platform before the first send.

Should you re-engage inactive subscribers first?

If a large part of your list has not opened in many months, run a re-engagement email from the old platform before moving. Import responders; drop or archive the rest. That keeps your new platform's early metrics clean. The re-engagement campaign guide has templates and timing.

Ongoing hygiene on the new platform

• Verify signups at the form if the platform allows custom forms or integrations.
• Remove long-term inactive subscribers with a sunset policy.
• Re-verify old segments before big sends.

Platform notes

Each platform handles imports its own way, and the details change, so read the current help pages before a large import. In general:

Platform	What to prepare
beehiiv	A CSV of active subscribers with any custom fields you use for segments; be ready to explain where subscribers came from if asked
Kit	A CSV with email and first name, plus tags or custom fields mapped on import
Substack	A CSV of email addresses; paid subscribers are handled separately from free ones

Whatever the platform, keep a copy of the original export, the cleaned file and the verification results. If a reviewer asks about the list, you can show where it came from and what you removed.

How much will cleaning remove?

That depends on the list's age and how it was collected. A list built through a confirmed signup form and mailed every week usually has few invalid addresses. A list collected years ago, or through a form with no protection, can have many more. Rather than guess, verify a random sample first with the email list sampler; the share of invalid and disposable addresses in the sample is a reasonable guide to the whole list.

If the sample shows a high invalid rate, that is also a signal about engagement: addresses that have gone dead usually sit next to many that are alive but no longer read. Plan a re-engagement step rather than importing everyone.

Clean your export before importing

Upload your active-subscriber export on the verify page; custom fields stay in the download for re-import. You get 100 free email checks when you sign in with Google, no card, enough to sample a large list or clean a small one.